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26650 and 18650 batteries which is better？

2019-06-10 11:50:06
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The 26650 lithium battery and the 18650 lithium battery are both cylindrical lithium batteries, and 18/26 indicates a diameter of 18 mm/26 mm, and 65 indicates a length of 65 mm, and 0 indicates a cylindrical battery.

Material system

At present, the mainstream material systems in the market mainly include lithium cobaltate, lithium manganate, nickel-cobalt-aluminum ternary, nickel-cobalt-manganese ternary, lithium iron phosphate, etc. The material system determines the operating voltage and unit capacity of the battery, and various material manufacturers. And the battery manufacturer improves the voltage and capacity of the whole battery by incorporating special materials, coating processes, and manufacturing process improvements in the materials; under normal circumstances, the working voltage and theoretical gram capacity of various materials are:

Lithium cobaltate 3.6V theoretical capacity is 274mAh/g

Lithium Manganate 3.7V theoretical capacity is 148mAh/g

Ternary material 3.65V theoretical capacity is 278mAh/g

Lithium iron phosphate 3.2V theoretical capacity is 170mAh/g

The various materials themselves will determine the cycle life of the battery, and the manufacturing level of the battery manufacturer will also affect the life.

Development status and historical reasons

The 18650 lithium battery was born in Japan's SONY company's first standard battery model. It was born at the material level and manufacturing level at that time. It is a combination of battery cost and performance balance. In notebooks, cameras, toys and lighting equipment, 18650 batteries have been very mature and stable after years of development; at the same time, because of its long history, it has formed a relatively mature market application.

With the development of new energy applications, the status of 18650 lithium battery has been gradually affected. Larger cylindrical lithium battery products and square battery products have appeared in the market in succession, such as 26650 lithium battery with relatively stable stability and consistency. 21700 lithium battery and square battery with various specifications. Square lithium-ion battery cells are mostly six-digit numbers and indicate the thickness, width and height of the battery, in millimeters, for example, 103450 or 10 (thickness) × 34 (width) × 50 (height) mm. The domestic automobile power batteries represented by BYD mainly use square batteries, and the material system is mainly lithium iron phosphate; Japanese and Korean enterprises mainly rely on cylinders in the power battery, and the ternary system is the main one.

Because the power battery needs thousands of batteries to be used together, it puts higher requirements on the consistency and safety of the battery products. The smaller the number of power battery system management batteries of the same capacity, the higher the relative safety and the longer the service life. Will increase. This puts higher requirements on the capacity of the power battery to reduce the use of the number of batteries, and to reduce the safety and life pressure of the power battery. Tesla is gradually phasing out Panasonic's 18650 lithium battery and turning to the larger 21700 lithium battery for the above reasons.

Application direction and trend

Combined with the excellent capacity characteristics and high consistency of the 26650 lithium battery, as well as the excellent structural design and mature manufacturing practice of the cylindrical battery, the 26650 lithium battery will gradually replace the 18650 lithium battery in the application of the power battery. And with the large-scale use of lithium batteries, the larger capacity of 26650 lithium battery to replace the 3C era of the tide 18650 lithium battery is bound to be the trend. At present, quite a number of PACK companies and 3C integrated application supply companies have begun to use 26650 lithium batteries, because the use of 26650 lithium batteries compared to the use of a larger number of 18650 lithium batteries, the cost of PACK can be reduced by about 30%, to improve the company's profitability and Market competitiveness is very impressive.